Odds of Hanging On
Once you have a job as a zookeeper, you have pretty great odds of sticking around for a long time—as long as you don't slack off. This means keeping up with the published research related to the animals you work with and giving each workday your best effort.
Your specific knowledge will keep the animals healthy and will keep you gainfully employed. Just make sure your daily interactions with the animals are, as Beyoncé would say, irreplaceable.